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CIRCULAR  NO.  126.  Issued  November  16,  1910. 

United  States  Department  of  Agriculture, 

BUREAU  OF  ENTOMOLOGY. 

L.  O.  HOWARD,  Entomologist  and  Chief  of  Bureau. 


INSECT  INJURIES  TO    THE    WOOD    OF    LIVING   TREES." 

By  A.  D.  Hopkins, 
In  Charge  of  Forest  Insect  Investigations. 

It  has  been  determined  that  insects  of  a  certain  class  attack  the 
wood  and  bark  of  living  timber  and  that,  while  they  do  not  con- 
tribute materially  to  the  death  of  the  trees  or  give  much  external 
evidence  of  their  presence,  they  produce  wounds  in  the  bark  and 
wormhole  and  pinhole  defects  in  the  wood  which  result  in  a  depre- 
ciation in  commercial  value  amounting  to  from  5  to  50  per  cent. 
These  defects  in  the  wood  are  not  detected  until  after  the  trees  have 
been  felled  and  the  logs  transported  to  the  mill  and  converted  into 
lumber.  Thus  to  the  actual  damage  to  the  lumber  is  added  the 
expense  of  logging  and  manufacture  of  the  defective,  low-grade 
material,  much  of  which  must  be  discarded  as  worthless  culls. 

The  oak  timber  worm. — One  of  the  most  destructive  of  the  class  of 
depredators  just  mentioned  is  the  oak  timber  worm.  It  enters  the 
wood  of  the  trunks  of  living  trees  through  wounds  in  the  bark  and 
at  the  base  of  broken  or  dead  branches  and  extends  its  "  pinhole  " 
burrows  in  all  directions  through  the  solid  heartwood.  The  losses 
occasioned  by  this  insect  in  the  hardwood  forests  of  the  eastern  United 
States  are  enormous  and  usually  affect  the  wood  of  the  finest  ex- 
amples of  old  trees. 

The  chestnut  timber  worm. — The  chestnut  throughout  its  range  is 
damaged  in  a  like  manner  by  the  chestnut  timber  worm.  Practically 
every  tree  of  merchantable  size  is  more  or  less  affected,  and  a  large 
percentage  is  so  seriously  damaged  that  the  product  is  reduced  to  that 
of  the  lowest  grade.  It  is  estimated  that  the  reduction  in  value  of  the 
average  lumber  product  at  any  given  time  is  not  far  from  30  per  cent, 

a  Revised  extracts  from  Bulletin  No.  58,  Part  V,  Bureau  of  Entomology,  U.  S. 
Department  of  Agriculture.     1909. 


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thus  involving  extensive  waste  and  an  increased  drain  on  the  forest 
to  supply  clear  lumber.  This  insect  also  attacks  the  oaks,  and  espe- 
cially the  red  oak,  the  older  trees  of  which  are  often  as  seriously 
damaged  as  are  the  chestnut. 

Garf  enter  worms. — The  oaks,  especially  the  white  oak  and  the  red 
oak.  are  seriously  damaged  by  carpenter  worms  of  the  genus  Prjon- 
oxystus.  The  holes  made  by  these  insects  through  the  heartwood  of 
the  best  part  of  the  trunks  are  sometimes  1.5  inches  in  diameter  one 
way  by  0.75  inch  the  other,  thus  causing  serious  damage  to  the  wood. 
These,  with  other  large  wood-boring  beetle  larva?,  sometimes  infest 
the  top  part  of  the  trunk  and  the  larger  branches  of  oak  trees,  where 
their  continued  work  results  first  in  the  dead  and  so-called  "  stasi- 
horn  "  top  and  subsequently  in  broken,  decayed,  and  worthless  trunks. 

Ambrosia  beetles. — One  of  the  commonest  defects  in  white  oak,  rock 
oak,  beech,  whitewood  or  yellow  poplar,  elm,  etc.,  is  that  known  to  the 
lumber  trade  as  "  grease  spots,"  "  patch  worm,"  and  "  black  holes." 
This  defect  is  caused  by  one  of  the  timber  beetles  or  ambrosia  beetles, 
which  makes  successive  attacks  in  the  living  healthy  sapwood  from 
the  time  the  trees  are  20  or  30  years  old  until  they  reach  the  maximum 
age.  Thus  the  black-hole  and  stained-wood  defect  is  scattered  all 
through  the  wood  of  the  best  part  of  the  trunks  of  the  trees.  The 
average  reduction  in  value  of  otherwise  best-grade  lumber  amounts, 
in  many  localities,  to  from  25  to  75  per  cent.  The  defect  is  commonly 
found  in  oak  and  elm  furniture  and  in  interior  hardwood  finish  in 
dwellings  and  other  buildings. 

The  locust  borer. — The  locust,  as  is  well  known,  suffers  to  such  an 
extent  from  the  ravages  of  the  locust  borer  that  in  many  localities  the 
trees  are  rendered  worthless  for  commercial  purposes  or  they  are 
reduced  in  value  below  the  point  of  profitable  growth  as  a  forest  tree ; 
otherwise  this  would  be  one  of  the  most  profitable  trees  in  the  natural 
forest  or  artificial  plantation  and  would  contribute  greatly  to  an  in- 
creased timber  supply. 

Turpentine  beetles  and  turpentine  borers. — While  the  softwood 
trees,  or  conifers,  suffer  far  less,  than  the  hardwoods  from  the  class 
of  enemies  which  cause  defects  in  the  living  timber,  there  are  a  few 
notable  examples  of  serious  damage.  There  is  a  common  trouble 
affecting  the  various  species  of  pine  throughout  the  country  known 
n-  basal  wounds  or  basal  fire  wounds.  It  has  been  found  that  a  large1 
percentage  of  this  injury  to  the  pine  in  the  States  north  and  west  of 
the  Gulf  State-  and  in  the  Middle  and  South  Atlantic  State-  LS 
caused  by  the  red  turpentine  beetle  and  in  the  Southern  States  by 

the  blaek"  turpentine  beetle.      These  beetles  attack  the  healthy  living 

baik-  at  and  toward  the  base  of  the  trunks  of  medium  to  large  trees 
and  kill  areas  varying  in  size  From  1  to  lo  square  feet.    These  dead 

[Cir.  126] 


areas  are  subsequently  burned  off  by  surface  fires  and  are  then  gen- 
erally referred  to  as  fire  wounds.  The  further  damage  to  the  ex- 
posed wood  by  successive  fires,  decay,  and  insects  often  results  in  a 
total  loss  of  the  best  portion  of  the  tree,  or  a  reduction  in  value  of  the 
lower  section  of  the  trunk  of  from  10  to  50  per  cent.  These  and 
similar  wounds  in  the  bark  of  trees,  including  those  caused  by  light- 
ning and  by  the  uncovering  and  exposure  of  the  wood  in  turpentin- 
ing, offer  favorable  conditions  for  the  attack  of  the  turpentine  borer, 
the  work  of  which,  together  with  that  of  two  or  three  others  with 
similar  habits,  is  very  extensive,  and  causes  losses  amounting  to  from 
10  to  50  per  cent  of  the  value  of  the  wood  of  the  best  part  of  the  trees 
thus  affected. 

The  white  pine  weevil. — The  abnormal  development  of  white  pine 
trees  as  the  result  of  successive  attacks  on  the  terminals  of  the  sap- 
lings and  young  trees  by  the  white  pine  weevil  is  an  element  of  loss 
of  considerable  importance,  especially  in  mixed  stands  and  in  open 
pure  stands  of  this  timber.  The  value  of  such  trees  is  reduced  from 
20  to  50  per  cent  below  those  of  normal  development,  and  there  is  an 
additional  loss  from  the  effect  of  their  spreading  branches  or  crowns 
in  the  suppression  or  crowding  out  of  trees  which  would  otherwise 
occupy  the  space  thus  usurped. 

There  are  many  other  examples  of  insects  which  damage  the  wood 
and  bark  of  living  trees,  but  those  mentioned  should  be  sufficient  to 
demonstrate  the  importance  of  insects  in  this  relation. 

CONTROL   OF    INSECTS   WHICH    CAUSE   DEFECTS    IN    LIVING   TIMBER.0 

The  class  of  insects  which  cause  defects  in  the  wood  of  living  timber 
can  be  controlled  to  a  greater  or  less  extent,  depending  upon  local  con- 
ditions, and  a  large  percentage  of  the  losses  prevented  through  the 
adoption  of  certain  requisite  details  in  forest  management,  among 
which  the  following  are  especially  important : 

(1)  The  utilization  of  all  of  the  defective  and  infested  timber 
that  will  pay  expenses  for  manufacture  into  merchantable  products, 
such  as  lumber,  cordwoocl,  etc. 

(2)  The  burning  of  infested  timber  and  waste  material  not  avail- 
able for  use,  including  dead  standing  and  fallen  timber,  to  remove 
the  breeding  places  of  insects  like  the  oak  timber  worm  and  the 
chestnut  timber  worm,  which  go  from  the  dead  to  the  living  timber. 

(3)  The  prevention  of  wounds  of  any  kind  in  the  bark  of  living 
trees. 

a  For   methods   of  controlling   the  locust   borer   and   white   pine   weevil,   see 
Circulars  S3  and  DO,  respectively,  of  the  Bureau  of  Entomology,  U.  S.  Depart- 
ment of  Agriculture. 
[Clr.  126] 


(4)  The  prevention  of  future  losses  by  the  practice  of  improved 
forestry  methods  to  eliminate  favorable  conditions  for  injury  and  con- 
tribute to  a  perpetual  supply  of  vigorous,  healthy  timber  to  be  utilized 
before  it  passes  the  stage  of  profitable  increment. 

It  should  be  remembered  that  the  different  species  of  insects  which 
cause  defects  in  the  wood  of  living  timber  require  different  details  in 
the  methods  of  control,  and  that  special  cases,  special  local  conditions, 
and  details  in  business  methods  and  requirements  determine  which 
one  of  the  available  methods  should  be  adopted. 

It  should  also  be  remembered  that  in  the  more  important  cases  much 
loss  of  time  and  money  may  be  prevented  and  the  best  success  attained 
by  first  securing  some  authoritative  advice  on  the  insects  involved 
and  the  specific  requirements  for  the  control  work. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture.  /I I II IIHI^IMinmnMI Uf7f f fflH llTli ? " ' ° A 

Washington,  D.  C,  October  7, 1910.  if / If ff // ff /// ||f //f f f f |f f f f f / //// /f f f ff / |f /I /////I //If 

[Cir.126]  3  1262  09228  3141 


